The invention relates to the preparation of ethylenically unsaturated emulsifiers, and also to the use of these emulsifiers in the preparation of emulsions of vinyl polymers in an aqueous phase.
Olefinically unsaturated monomers in aqueous dispersion can be polymerized to form emulsions of an addition polymer or copolymer. Emulsions of this type are often used in the preparation of paints and lacquers. The emulsions can be obtained by polymerizing one or more monomers in an aqueous phase in the presence of a suitable catalyst system and in the presence of necessary emulsifiers, stabilizers and/or protective colloids and other additives.
The emulsifiers are required to disperse the monomers in the water and to keep the resulting polymer particles in the emulsified state. In most cases, emulsifiers are employed that cannot copolymerize with the monomers used. It has been proposed to use emulsifiers containing ethylenically unsaturated groups, so that they can be incorporated into the polymer. These emulsifiers possess a sulphonic-acid group or a sulphonate group, as a hydrophilic group. See U.S. Pat. No. 3,392,147 in this regard. The disadvantage of these emulsifiers is their limited hydrolysis-stability. Certain of these emulsifiers are, furthermore, characterized by a low polymerization rate. Moreover, these emulsifiers give rise to yellowing of the coatings obtained by using the aforementioned emulsifier-modified polymers.